Check « Constraints « SQL Server / T-SQL Tutorial

7.5.1.Using CHECK Constraints
7.5.2.Adding a CHECK Constraint to an Existing Table
7.5.3.Constraints with name
7.5.4.CHECK Clause
7.5.5.Check Constraint
7.5.7.A check constraint uses an expression to qualify records that are acceptable for any Inserts or Updates
7.5.8.Use or to link two conditions for check constraint
7.5.9.Using a Multicolumn CHECK Constraint

7.5.10.Check for data length
7.5.11.Pattern based constraint
7.5.12.Mark nocheck for a constraint
7.5.13.A table-level check constraint that limits Banker IDs to a specific format